All this time, Aliens: Colonial Marines' stupid AI may have been caused by a single typo

Five years later, one modder uncovers the smoking 'a'. Was a single letter really the problem?

Aliens: Colonial Marines released on February 11, 2013. It wasn't very good. As Chris Thursten noted in our review, the AI of the aliens was especially bad. At the time, he said, "aliens pop out of vents and pop back in again, get stuck on the ceiling, fall off walls and run in circles." Well, it turns out the game's laughably stupid xenomorphs may have been caused by a typo—more specifically, a single letter mucking up the game's code.

As ModDB user jamesdickinson963 explained in a recent post, a line of code in one of the game's .INI files has a small but serious typo. This was spotted by poster JigglesBunny on Resetera, so we decided to investigate. Note the unneeded 'a' in 'tether' in the second line of this snippet:

In theory, fixing this typo could correct the erratic behavior of the xenomorphs. But to what degree? After confirming the code does indeed have a typo, I tried the fix for myself to find out.

Here's how the xenomorphs behave to begin with. As Chris said in his review, they're all over the place, they're sluggish, and all around they come across as kinda dopey.

Now look at how they behave after fixing the typo. In my experience, they're not only considerably more aggressive, they're also much better at tracking the player. As an experiment, I tried just running away from one, a maneuver which would normally confound a xenomorph, and it stayed right on my tail.

The change is less noticeable in some situations, and it's tough to say just from playing how much of the xenomorphs' clumsiness was caused by this typo, but they certainly seem to move more efficiently once it's corrected. They waste less time getting to the player, crawl and lunge more often, and generally move in more of a beeline rather than their usual drunken stroll. I mean, they're still plenty dopey, but hey, what did you expect?

This isn't the first time we've seen AI buggered by a small typo. Earlier this year, Civilization 6 developer Firaxis confirmed that a spelling error in one of the game's data files was messing with the way AI leaders allocate resources.